0 %R or %T at 350nm

A sensor reading 0 at 350nm can usually only be remedied by increasing signal levels or replacing the sphere, this is a different issue than reading 0 at any other wavelength. Technically 350nm and 355nm have no weighting in all the Observer tables so your Tristimulus and Scale and Index results are not affected by this issue.

If you notice an unexpected 0 %R or %T at any wavelength above 420nm then suspect a communication error between the LSUP and SPSP boards in the sensor.

If you notice a long string of 0's from 350nm to 400nm or up to 420nm then check the UV Filter position as it may be inserted into the light path.